V tabulce organizace zkuste
return $this->hasManyThrough('App\..path-to..\User', 'App\..path-to..\Organisation_Users_Roles', 'organisation_id', 'id' );
V tabulce organizace zkuste
return $this->hasManyThrough('App\..path-to..\User', 'App\..path-to..\Organisation_Users_Roles', 'organisation_id', 'id' );